Polar Bear, Ursus maritimus, Predation on Belugas, Delphinapterus leucas, in the Bering and Chukchi Seas

LLOYD F. LOWRY,1 JOHN J. BURNS1 and ROBERT R. NELSON2

1Alaska Department of Fish and Game, 1300 College Road, Fairbanks, 99701 2Alaska Department of Fish and Game, Box 1148, Nome, Alaska 99762

Lowry, Lloyd F., John J. Burns, and Robert R. Nelson. 1987. Polar Bear, Ursus maritimus, predation on Belugas, Delphinapterus /eucas, in the Bering and Chukchi seas. Canadian Field- Naturalist 101(2): 141 - 146. Two incidents of Polar Bear predation on Belugas which occurred off the coast of western Alaska in April 1984 are described. A single subadult Beluga was killed at a small lead in the , probably by a female bear with three cubs, and at least 40 whales were killed at an ice entrapment by one or more bears in the northern Bering Sea. A review of such occurrences off Alaska, Canada, and Eurasia indicates that Belugas are normal prey of Polar Bears. Bear predation may occur when whales are entrapped by ice or while unrestrained whales are passing through leads or surfacing at holes in deteriorating ice sheets. Bear predation probably has little effect on Beluga populations, although it may be of occasional significance at entrapments when many whales are killed that eventually would have been released. Belugas are large in comparison to other potential prey and may be of some local importance in Polar Bear diets. Key Words: Polar Bear, Ursus maritimus, Beluga, De/phinapterus leucas, predation, Alaska.

Although it is generally recognized that Polar During a flight over the flaw zone on 27 April, we Bears, Ursus maritimus, may at times prey on Belugas sighted a female Polar Bear accompanied by three (white whales), Delphinapterus leucas (e.g. Tomilin one-year-old cubs. Blood was evident on the cubs'fur, 1957; Kleinenberg et. al. 1964), there are no published so we circled to examine the area. A large Polar Bear records of such occurrences in the waters off Alaska. was feeding on the carcass of a Beluga about 300 We present observations of Polar Bear predation on meters from the sow and cubs. We landed and Beluga Whales in the Bering and Chukchi seas, examined the carcass and kill site (68°54.9'N, describe the environmental circumstances surround­ 166°48.5'W). ing the events, and discuss the possible significance of The carcass was on a large piece of thick ice that this phenomenon. formed one edge of a lead that had numerous medium-sized floes adrift in it (Figure 1). With the Observations exception of some very small openings, the area During spring of 1984, a marine mammal research between the floes was filled with thin ice and slush. An program was conducted in the eastern Chukchi Sea obvious trail of blood led from the carcass to the edge near Cape Lisburne, Alaska. Field operations of the lead where it ended in slush ice. It was unclear included helicopter flights over the shorefast ice, flaw exactly where the kill had been made. However, when zone, and drifting pack ice. Below-normal tempera­ we later searched the area from the air, we located a tures prevailed in the area throughout the first part of patch of blood-stained snow and numerous bear April. The low temperatures followed almost a month tracks on a floe that was drifting slowly up the lead, of above-normal temperatures and resulted in about 150 meters from where the blood trail ended. continual freezing of leads. On 24 April open water The bear had apparently caught the whale from the areas appeared in the flaw zone and rapidly developed drifting ice when the floe was against the edge of the into an extensive lead system. Hundreds of Belugas lead, pulled the whale onto the floe, then dragged it were seen moving northward through the leads from onto the more stable ice. 25 to 27 April. The leads were again mostly refrozen The carcass was that of a young Beluga (standard from 29 April to 3 May. During this period whales length 230 cm), probably 2 years old. The skin and were occasionally sighted in small cracks and under blubber had been entirely removed from the head and thin ice. Impressions of Belugas, made when thin ice torso but was still intact on the flukes. A detached formed over the backs of stationary whales, were seen section of skin (about 60 by 100 cm) was near the throughout the flaw zone. The leads reopened on 4 carcass. All of the blubber had been chewed or May and Belugas were seen moving northward from scraped off that piece of skin. The chest and then until our observations ended on 13 May. abdominal cavities had been opened but all organs

141 142 THE CANADIAN FIELD-NATURALIST Vol. 101

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FIGURE I. Diagram of the area where a Polar Bear killed a Beluga in the eastern Chukchi Sea, 27 April 1984. were intact. Both front flippers and some ribs were Little Diomede (approximate pos1t1on 65°48.2'N, missing, and the muscle of the axial skeleton had been 168° 54.0'W). An estimated 30 Polar Bears were removed to the bone. The lower jaw was broken. The scavenging carcasses of Belugas that were scattered carcass was not frozen although the air temperature at around the opening in the ice. the time was -l0°C. We also received reports of Polar Bear predation on The second instance of predation also occurred in Belugas in the southern Chukchi Sea in April 1984, the spring of 1984. Bears and dead whales were first but we were unable to document the circumstances seen and photographed on 24 April from an airplane through personal examination or photographs. The flying just south of , between Fairway first report was from people snowmachining in the Rock and Little Diomede Island (approximate vicinity of Cape Thompson (68°08'N, l66°00'W) who location 65°41.5'N, 168°45.0'W). At that time it was saw where Polar Bears had killed "at least" one Beluga reported that there were 15 Polar Bears and a large (Roland Quimby, personal communication). The number of carcasses longer than 2 meters spread second report was from a pilot (David Furber, around a hole in the ice (John Fray, personal personal communication), who reported seeing communication). A diagram of the situation was numerous Belugas in two small holes in an area of constructed from photographs (Figure 2). It was extensive refrozen leads (approximate position difficult to identify all Beluga carcasses because many 67° 49'N, 165° l 5'W). Several Polar Bears and several were partially covered by drifting snow or obscured by dead Belugas were on the ice nearby. ice ridges. Nevertheless, counts indicated a minimum of 40 Belugas on the ice, and an additional 12 to 15 Discussion possible carcasses. Most of the carcasses had been fed Prior to 1984 we received few reports of Polar Bear upon only minimally, and appeared to be of gray, predation on Belugas in the Bering and eastern subadult animals. Five bears visible in the Chukchi seas. On 26 March 1967, Robert Curtis saw a photographs were all medium to large animals. The dead Beluga on the ice in the southern Chukchi Sea pilot reported that at the time of the sighting there that he said had been caught and partially eaten by a were numerous leads nearby, and open water was Polar Bear (personal communication to Francis H. visible in the photographs at a distance of about l km. Fay). Nelson Walker, who for many years was The kill site was observed again on 6 May by engaged in guiding Polar Bear hunters in the central residents of Little Diomede Island (Little Sister Chukchi, often saw small groups of Belugas Joseph Alice, personal communication). By that time entrapped by ice in the region west of 168° W the ice had drifted to a location about 4 km north of longitude (personal communication). Bears hunted at 1987 LOWRY, BURNS, AND NELSON: POLAR BEAR PREDATION 143

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FIGU RE 2. Diagram of the area where Polar Bears killed Belugas in the northern Bering Sea, April 1984. many ofthe entrapments, and up to seven dead whales There are few reports describing interactions of were seen. On 15 May 1979, in the northeastern Polar Bears and Belugas in the eastern Canadian Chukchi Sea near Point Barrow(71°01'N, 157°25'W), . Degerb¢1 and Freuchen (1935) reported that Don K. Ljungblad (personal communication) saw bears were known to attack Belugas entrapped in ice four Polar Bears, two of which were feeding on a in Baffin Bay. Freeman (1973) provided an interesting Beluga carcass, while a third was pulling a whale out description of an event that occurred in March 1970 of the water through very thin ice. The kills had been near the southeastern tip of Ellesmere Island. Local made at the north end of a narrow lead. An estimated hunters reported that a medium-sized female Polar 40 to 60 Belugas were milling about in a wider portion Bear had caught and removed three Belugas (one of the lead just to the south. Ar.other occurrence was subadult, one adult female, and one adult of unknown documented by a photograph in Mitchell and Reeves sex) from a small open water area alongside a partially (1981) taken on 12 July 1975 in the Beaufort Sea grounded iceberg. Wh~n Freeman visited the site approximately l 10 km north of the Mackenzie River some days later at least two other bears had been in the delta which shows a subadult Beluga lying on a area, and two of the Beluga carcasses had deteriorating ice floe near a small hole. Two Polar disappeared, apparently having fallen into the water. Bears were feeding on the carcass when it was located, Hey land and Hay ( 1976) examined a stranded juvenile and numerous Belugas were seen a few kilometres Beluga in Cunningham Inlet, Somerset Island, that away surfacing in holes in similar ice. had deep, healed, parallel scars on the posterior 144 THE CANADIAN FIELD-NATURALIST Vol. 101 portion of the body that they thought were probably predation do occur, bears are rarely successful in inflicted by a Polar Bear. They also noted that Polar catching whales and Belugas therefore do not make up Bears had once attacked captive Belugas being held in a significant part of their summer diet. a tank at Churchill, Manitoba. Smith (l985), also Predation at entrapments appears to be the most working in Cunningham Inlet, reported nine sightings widespread and common type. However, Brodie of Belugas with wounds that were ascribed to Polar (l 982) observed that the travel patterns and Bears. establishment of settlements of Canadian have We are aware of only two published records of evolved such that they take advantage of locations Polar Bear predation on Belugas in Eurasian waters, where whales may become entrapped. This creates a both from the vicinity of Novaya Zemlya. Tomilin bias in that reports of entrapment are more common ( 1957) stated that hunters there once found a group of near inhabited and travelled areas. Also, savssat are 34 Belugas trapped near shore by ice. Three whales reportedly easy to detect due to condensing vapors that had apparently been killed by bears were on the from the open water and breathing of the animals ice. Kleinenberg et al. (l964: p. 370) described an (Porsild J9 J8), and the noise whales make when incident that occured in 1940 as follows: "They saw surfacing (Vibe 1950). The success of Polar Bears that the bear was lying at the end of an ice floe with hunting entrapped Belugas is virtually assured, and outstretched paws, and that the water in the hole was large numbers of whales may sometimes be killed. billowing with agitated Belukhas. As soon as a Predation that occurs at leads or holes in Belukha came to the surface near the bear, it received deteriorating ice may be much less easily observed for a crushing blow on the head, and the Belukha, several reasons. An event is more likely to involve a weighing several hundred kilograms, was dragged on single bear and a single whale, and evidence of the kill the ice. Thirteen Belukhas lay near the bear, but he did may be obscured by moving ice or drifting snow. Also, not cease killing." predation may occur far from villages or travel routes These observations confirm that Polar Bears are on the ice and will go undetected unless the kill site is capable of capturing and killing Belugas. Bear seen from an aircraft at low altitude. It is likely that predation may occur in three basic environmental hunting success of bears attempting to catch free­ settings. The first is in situations where whales are ranging Belugas in the ice is relatively low overall. The 1 entrapped in ice, which have been termed savssats • probability of successful capture will vary with ice Such entrapments may be of long duration - for conditions and the abundance of whales and bears in example when whales fail to move to favorable areas specific areas. Belugas that migrate through the lead prior to extensive freeze-up in the fall (Hill 19672; system off western Alaska on their way to the eastern Freeman 1968), or of short duration when the Beaufrrt Sea number at least l J 500 (Davis and Evans movement of whales is temporarily restricted due to J9823). Their migratory path passes through areas ice conditions. The other two settings involve free­ where we have regularly observed large numbers of ranging Belugas moving through narrow lead systems Polar Bears. In our opinion, successful predation by (e.g. our observation from off Cape Lisburne) or bears on Belugas in the northern Bering and Chukchi surfacing in holes in deteriorating ice sheets (Mitchell seas probably occurs annually during the spring and Reeves 1981 ). These settings are similar in that the migration, simply because of the numerous whales' access to air is restricted to small areas of open opportunities for such interactions. In 1984, warm water where bears can hunt more effectively. temperatures during March allowed the northward Polar Bears and Belugas may also interact in migration to begin as usual. Cold temperatures during shallow, ice-free areas, where many whales April impeded the migration, causing some spend the summer. Smith ( 1985) made detailed temporary entrapments, and also resulted in large observations in one such area (Cunningham Inlet), aggregations of whales which passed Cape Lisburne in and considered that although opportunities for pulses when. the leads were open. These conditions

1Porsild (1918) described ice entrapment of marine mammals and introduced the anglicized Greenland Inuit term savssats (pronounced s'sets) into the scientific literature. According to Schultz-Lorentzen ( 1927) savssat is plural and refers to "whales or seals locked in a hole in the ice." The singular savssaq refers to one entrapped animal. In Alaska the equivalent words used by Inuit living in the area from Bering Strait to Point Hope are sapraq (singular) and saprat (plural). 2R. M. Hill. 1967. Observations on beluga whales trapped by ice in Eskimo Lakes winter 1966 / 67. Inuvik Research Laboratory Report, Inuvik, N.W.T. 3Davis, R. A., and C. R. Evans. 1982. Offshore distribution and numbers of white whales in the eastern Beaufort Sea and Amundsen Gulf, summer 1981. Report by LGL Limited, Toronto, Ontario, for SOHIO Alaska Petroleum Co. Anchorage, Alaska, and Dome Petroleum Limited, Calgary, Alberta. 78 pp. 1987 LOWRY, BURNS, AND NELSON: POLAR BEAR PREDATION 145 may have enhanced the success of Polar Bears hunting Polar Bears (Mitchell and Reeves 1981 ). Both Belugas Belugas. and Narwhals should be considered as components of Without further quantification, it is not possible to the diet of Polar Bears, with their importance, relative fully assess the significance of bear predation on to other prey species, depending on environmental populations of Belugas. Predation at leads and holes conditions and patterns of distribution and may involve mostly subadult whales, and is probably abundance. infrequent and of minimal significance. At entrap­ ments, on the other hand, bears may kill many Acknowledgments animals, both subadults and adults. In situations Our observations were made during studies funded where whales would have perished due to prolonged by the NOAA Outer Continental Shelf Environmen­ entrapment in severe ice conditions during winter, tal Assessment Program. Preparation of the predation would not increase the level of mortality but manuscript was supported by the Alaska Department only change the cause. In situations where whales of F ish and Game and the Federal Aid in Wildlife would have escaped from temporary entrapment, Restoration Program. We thank the following people mortality due to predation would be additive. Since for allowing us to use their unpublished observations: people hunt savssat there is little information on Little Sister Joseph Alice, Robert Curtis, John Fray, natural survival (Mitchell and Reeves 1981 ). It is, David Furber, Don Ljungblad, Roland Quimby, and however, inappropriate to assume that all such Nelson Walker. Without such keen observers our confinements are fatal, as there is evidence that even attempts at understanding northern marine mammals after long periods of entrapment whales may survive would be much less fruitful. Ann Adams, Leon Kelly and eventually escape to more favorable areas (Vibe and Robert LaBonty provided invaluable assistance 1950; Freeman 1968). Based on the photographs we during field operations in the Chukchi Sea. We thank examined, whales entrapped in the northern Bering Kathryn Frost for her careful review of the Sea in 1984 would have escaped when nearby leads manuscript, and anonymous reviewers for their opened. comments. A final consideration is the possible importance of Belugas in the diet of Polar Bears. The prey of Polar Literature Cited Bears in the Canadian Arctic is primarily the Ringed Best, R. C. 1977. Ecological as pects of polar bear nutrition. Seal (Phoca hispida) and, secondarily, the Bearded Pages 203- 211 in Proceedings of the 1975 Predator Seal (Erignathus barbatus)) (Stirling and Archibald Symposium. Edited by R. L. Phillips and C. Jonke!. 1977; Smith 1980). There have been no comprehensive University of Montana, Missoula. Brodie, P. F. 1982. The beluga (Delphinapterus leucas); studies of the diet of Polar Bears in Alaska. During growth at age based on a captive specimen and a our operations at Cape Lisburne in April-May we discussion of factors affecting natural mortality estimates. examined seven Polar Bear kill sites. In addition to the Report of the International Whaling Commission 32: Beluga already described, those included two Ringed 445 - 447. Seals, three Bearded Seals, and a group of five eider Degerb~I M., and P. Freuchen. 1935. Mammals. Report of ducks (Somateria sp.). Best (l977) estimated that a the Fifth Thule Expedition 1921 - 24. The Danish Ringed Seal weighing 27.8 kg could supply the energy Expedition to Arctic North America in charge of Knud requirements of a 229 kg Polar Bear for 6.4 days. Rasmussen, Ph.D. Volume 2, numbers 4- 5. 278 pp. Assuming that the composition of the animals is Freeman, M. M. R. 1968. Winter observations on Beluga (Delphinapterus leucas) in Jones Sound, N. W.T. similar, an average Beluga, which may weigh 600 kg, Canadian Field-Naturalist 82: 276- 286. could provide the equivalent of 140 days of Freeman, M. M. R. 1973. Polar bear predation on beluga nourishment. Our observations, and those of others, in the Canadian Arctic. Arctic 26: 163. indicate that when many Belugas are killed they are Heyland, J. D., and K. Hay. 1976. An attack by a polar only partially eaten, while when only one whale is bear on a juvenile beluga. Arctic 29: 56- 57. caught it may be entirely consumed. While the Kleinenberg, S. E., A. V. Yablokov, B. M. Belkovich, and potential importance of Belugas in the diet of Polar M. N. Taresevich. 1964. Beluga(Delphinapterus leucas): Bears is clearly large, due to the difficulty of hunting Investigation of the species. lzdatel'stvo Nauka, Moscow. free-ranging whales and the sporadic nature of [Translated from the Russian by Israel Program for Scientific Translations, 1969. Available from National savssat, this importance is probably rarely realized. It Technical Information Service, U. S. Department of is possible, however, that the hunting stategy of Polar Commerce, Springfield, Virginia 22151]. Bears in some areas may take advantage of places Mitchell, E., and R. R. Reeves. 1981. Catch history and favorable for capturing Belugas. There are also cumulative catch estimates of initial population size of several records of Narwhals (Monodon monoceros) cetaceans in the eastern Canadian arctic. Report of the found dead on the ice, presumably due to predation by International Whaling Commission 31: 645- 682. 146 THE CANADIAN FIELD-NATURALIST Vol. 101

Porsild, M. P. 1918. On "savssats": a crowding of arctic Tomilin, A.G. 1957. Cetacea. Volume 9. In: Mammals of animals at holes in the sea ice. Geographical Review 6: the USSR and adjacent countries. Edited by V. G. 215 - 228. Heptner. Izdatel'stvo Akademii Nauk SSSR, Moscow. Schultz-Lorentzen, C. W. 1927. Dictionary of the West [Translated from the Russian by Israel Program for Greenland and Eskimo Language. Meddelelser om Scientific Translations, 1967. Available from Na ti on al Gr~nland 69: 1- 303. Technical Information Service, U. S. Department of Smith, T. G. 1980. Polar bear predation of ringed and Commerce, Springfield, Virginia 22151]. bearded seals in the land-fast sea ice habitat. Canadian Vibe, C. 1950. The marine mammals and marine fauna of Journal of Zoology 58: 2201 - 2209. the Thule District (northwest Greenland) with observa­ Smith, T. G. 1985. Polar Bears, Ursus maritimus, as tions on ice conditions in 1939- 41. Meddelelser om predators of Belugas, Delphinapterus leucas. Canadian Gr~nland 150(6): 1- 115. Field-Naturalist 99: 71 - 75. Stirling, I., and W.R. Archibald. 1977. Aspects of predation of seals by polar bears. Journal of the Fisheries Received I August 1985 Research Board of Canada 34: 1126- 1129. Accepted 15 January 1986